[PATCH v29 17/32] mm: Fixup places that call pte_mkwrite() directly

Yu-cheng Yu
2021-08-20T18:20:41Z

When serving a page fault, maybe_mkwrite() makes a PTE writable if it is in
a writable vma. A shadow stack vma is writable, but its PTEs need
_PAGE_DIRTY to be set to become writable. For this reason, maybe_mkwrite()
has been updated.

There are a few places that call pte_mkwrite() directly, but have the
same result as from maybe_mkwrite(). These sites need to be updated for
shadow stack as well. Thus, change them to maybe_mkwrite():

- do_anonymous_page() and migrate_vma_insert_page() check VM_WRITE directly
and call pte_mkwrite(), which is the same as maybe_mkwrite(). Change
them to maybe_mkwrite().

- In do_numa_page(), if the numa entry was writable, then pte_mkwrite()
is called directly. Fix it by doing maybe_mkwrite(). Make the same
changes to do_huge_pmd_numa_page().

- In change_pte_range(), pte_mkwrite() is called directly. Replace it with
maybe_mkwrite().

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
---
v25:
- Apply same changes to do_huge_pmd_numa_page() as to do_numa_page().
---
mm/huge_memory.c | 2 +-
mm/memory.c | 5 ++---
mm/migrate.c | 3 +--
mm/mprotect.c | 2 +-
4 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c8dd5913884e..b9a6fc7af693 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1515,7 +1515,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
pmd = pmd_modify(oldpmd, vma->vm_page_prot);
pmd = pmd_mkyoung(pmd);
if (was_writable)
- pmd = pmd_mkwrite(pmd);
+ pmd = maybe_pmd_mkwrite(pmd, vma);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
diff --git a/mm/memory.c b/mm/memory.c
index 25fc46e87214..5f8a84c17fa6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3781,8 +3781,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)

entry = mk_pte(page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
- if (vma->vm_flags & VM_WRITE)
- entry = pte_mkwrite(pte_mkdirty(entry));
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);

vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
@@ -4416,7 +4415,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
pte = pte_modify(old_pte, vma->vm_page_prot);
pte = pte_mkyoung(pte);
if (was_writable)
- pte = pte_mkwrite(pte);
+ pte = maybe_mkwrite(pte, vma);
ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
update_mmu_cache(vma, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
diff --git a/mm/migrate.c b/mm/migrate.c
index 7e240437e7d9..8c90eb4ab3b1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2794,8 +2794,7 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
}
} else {
entry = mk_pte(page, vma->vm_page_prot);
- if (vma->vm_flags & VM_WRITE)
- entry = pte_mkwrite(pte_mkdirty(entry));
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
}

ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 883e2cc85cad..9b424f2fd3a9 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -135,7 +135,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
if (dirty_accountable && pte_dirty(ptent) &&
(pte_soft_dirty(ptent) ||
!(vma->vm_flags & VM_SOFTDIRTY))) {
- ptent = pte_mkwrite(ptent);
+ ptent = maybe_mkwrite(ptent, vma);
}
ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
pages++;
--
2.21.0